head to head
Rock Band 2 asks more than Space Channel 5: Part 2, and the gap is execution.

Execution · Pure Mechanics
The full-band rhythm game whose setlist and feel made it the genre's high-water mark.

Execution · Practiced Mastery
A stylish call-and-response rhythm adventure where reporter Ulala dances to save the galaxy.
Rock Band 2 leans Execution (Pure Mechanics); Space Channel 5: Part 2 leans Execution (Practiced Mastery).
Rock Band 2 leans clearly harder on execution.
Rock Band 2
Guitar, drum, and vocal accuracy on expert charts
Space Channel 5: Part 2
Precise timing on call-and-response button sequences
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Rock Band 2
Charts never respond
Space Channel 5: Part 2
Sequences are scripted
Space Channel 5: Part 2 leans a little harder on variance, though the gap is small.
Rock Band 2
Fixed setlist charts
Space Channel 5: Part 2
First playthrough hides upcoming commands
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Rock Band 2
Overdrive activation paths decide leaderboard scores
Space Channel 5: Part 2
Memorizing every routine for perfect runs
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.